"Maintenance SLOVENIJA and recovery 2014 of HV electricity transport systems and aerospace assistance" STATE-OF-THE-ART FOR DYNAMIC LINE RATING TECHNOLOGY Future Vision Kresimir Bakic, CIGRE & ELES, Slovenia Beograd, 6 November 2014 1
Plan of presentation 1. INTRODUCTION Why we need DLR? 2. POSIBLE SENSORS FOR DLR 3. WHAT IS THE KEY ISSUE FOR LINE MONITORING? STATIC VALUE, DYNAMIC VALUE, +++ PREDICTIONS 4. TECHNOLOGY BASED ON WEATHER STATIONS 5. TECHNOLOGY BASED ON TENSOR CELLS 6. TECHNOLOGY BASED ON CONDUCTOR TEMPERATURE 7. TECHNOLOGY BASED ON CONDUCTOR VIBRATION 8. TECNOLOGY BASED ON FIBER OPTIC 9. TECHNOLOGY BASED ON SAG MONITORING DEVICE 10. TECHNOLOGY BASED ON DGPS SATTELITE MONITORING 11. MY VISION ON SATELLITE AIDED OHL MONITORING - CONDUCTOR: SAG, TEMPERATURE, ICING - TOWER: TENSION, SAG - CORRIDOR: VEGETATION MANAGEMENT - WEATHER CONDITION??? GROUND LEVEL WIND FLOW??? - RECOVERING SUPPORTS DURING LARGE WEATHER STORMS, SPACE STORMS 2
CAPACITY INCREASE INTRODUCTION Why we need DLR? - DLR solution - cheapest - Older OHLs with high loads - Carefuly with losses 300% TECHNOLOGIES FOR INCREASING CAPACITY OF OHLs 1 Real Time Monitoring 2 Probabilistic Rating 3 Conductor Retention 4 Conductor Change 5 Voltage Increase 6 Conversion to DC 200% 6 5 New HTLS conductors (ACCC) could be more competitive than investment in non-reliable monitoring. 100 % 4 1, 2 3 0 25% 50% COST Base Case: New Line: Cost = 100% Capacity=100% 75% CIGRE WG B2/C1-19 100% 3
INTRODUCTION Criteria for decision of Technology 1. ECONOMY 2. RELIABILITY (supply method, ICT transmission) 3. ACCURACY (± 5 A) and for SAG (± 20 cm) 4. PLACING (with or without switching off line) Economy of cable or OHL Capacity of Cable or OHL Source: CIGRE WG B2/C1-19 4
TECHNOLOGIES FOR OHL MONITORING Main parts of technology: - sensors, - information transmission. Monitoring of - electrical, thermal, mechanical and atmospheric parameters. SENSORS TECHNOLOGIES: - optical, infrared, ultra-violet, satellite imagery, - surface acoustic waves (SAW), - vibration sensors, conductor temperature sensors, - LIDAR (Laser Imaging Detection And Ranging), - tensor load cells, strain sensors, - wind measure with ultrasonic anemometers, etc. Source: EPRI, Future Inspection of OHL, 2008 5
Thermal balance equation Imaginary Boundary Representing Sky and Surrounding Sky or Diffuse Solar Radiation Direct or Beam Solar Radiation p r Portion Not Absorbed by Conductor Wind Under Steady p p p p p j j s c r p s p c State p - Joule heating - Solar heating W W W - Radiation cooling W m m m - Convection cooling r Condition W m m p s p c Horizontal Conductor Oriented in Air with Wind Normal to Conductor 2 I R Main atmospheric parameters are wind, wind direction, ambient temperature and solar 6
Temperature in atmosfere 7
WHAT IS THE KEY ISSUE FOR LINE MONITORING? Ampacity of a conductor is that maximum constant current which will meet the design, security and safety criteria of a particular line on which the conductor is used. Static rating is the simplest thermal rating system based on ampacity Tables provided by the conductor manufacturer or calculated based on worst weather case. Using such tables, the normal or continuous thermal rating of each conductor is specified for certain weather conditions and conductor parameters. STATIC VALUE Conservative approach based on worst weather case. Conditions for conservative thermal ratings: 1) Wind speed: 0,6 m / s perpendicular wind, 2) Ambient temperature 30-35 0 C, 3) Solar radiation 900-1000 W/m 2 ; 4) Conductor absorptivity 0.5 0.6 DYNAMIC VALUE Real-time monitoring many different technologies. Some technologies more effective during system normal operation and other during system contingency. Global error margin for real-time rating acceptable for operators should be ± 10%. PREDICTIONS Real added value for monitoring systems. Key issues related to wind predictions in the OHL corridor 8 in so different terrains.
GOOD TO KNOW From CIGRE brochure 299 Guide for selection of weather parameters for bare overhead conductor ratings : The average temperature of a line section will not exceed the maximum design temperature by more than 10 C, even under exceptional situations, and will provide a confidence level of at least 99% that the conductor temperature will be less than the design temperature when the line current equals the line rating. The highest local conductor temperature will not exceed the maximum design temperature by more than 20 C when the line current equals the line rating. Because ratings based on probabilistic clearances require consideration of other criteria than weather parameters (load probabilities, traffic under the lines etc.) their application is not included in this document. This and other related documents discuss sag and tension calculations only in a general manner. The document recognizes that maintaining adequate clearances is usually the primary objective of line ratings and that conservatism in sag calculations can mitigate the consequences of too optimistic rating assumptions. Yet, such combination may not be applicable in all circumstances. For ensuring adequate clearances, it is recommended that the transmission 9 owner verifies their actual line clearances at appropriate intervals.
STATIC RATING 1m/s 2m/s 0.6m/s Static rating Source: from CIGRE JWG C1-B2-19 Static rating 10
TECHNOLOGIES FOR THERMAL OHL MONITORING -Ampacimon (vibration) Weather sta. Load cell (Tensor) Surface Acoustic Waves (SAW), Conductor surface temperature DONUT Source: from CIGRE TB 498 11
1. TECHNOLOGY BASED ON WEATHER STATIONS RTM system Calculating in-span Conductor temperature from a weather station. (CIGRE Bros. 207) Weather station in ROW The purpose of real-time monitoring is to determine, in real-time, the position of the conductor in space Indirect Method 12 conductor replica (SHAW technologies)
2. TECHNOLOGY BASED ON TENSOR CELLS RTM system SOURCE: CIGRE TB 498 13
3. TECHNOLOGY BASED ON CONDUCTOR TEMPERATURE RTM system DONUT device clamped on conductor of OHL Temperature on surface of conductor Other type of conductor temperature is fiber optic measurement inside conductor. (4) 14 SOURCE: CIGRE TB 498, from 2012
5. TECHNOLOGY BASED ON SAG MONITORING DEVICE RTM system camera target 15 SOURCE: CIGRE TB 498, from 2012
6. TECHNOLOGY BASED ON VIBRATION SENSOR Principles behind Ampacimon Fundamental Frequency [Hz] Sag [m] 0.1367 ± 4 10-4 16.40 ± 0.1 Ampacimon detects low frequencies (accelerometers) The sag is determined via the main vibration mode Only the frequency is needed, not the amplitude No calibration is required The accuracy of the measured sag depends on the sampling frequency (approximately 2%) Measurements are processed using the Fourier transformations method 16
Technology Use Where/how? How long? Weather station wide No switch off 30 years Load cell (Tensor) USA, EU Switch off line On tower Conductor surface temperature (Donut) Conductor inside temperature (Optical fiber) Sag measures (video, satellite imagery) Conductor vibration (Ampacimon) TECHNOLOGIES FOR THERMAL OHL MONITORING comparison limited limited limited Pilot projects Switch off line On conductor in suitable span Switch off line In conductor. No switch off Markers Switch off line On conductor in suitable span 20 years 20 years 10 years 10 years 5 years 17
TECHNOLOGY BASED ON DIFFERENTIAL GLOBAL POSITIONING SATELLITE (DGPS) Method for measure sag by DGPS. Capable of measuring sag to accuracy of appr. 25 mm using commercially available GPS. Method measures conductor to ground based on altitude information obtained from GPS device. 18 Weakness of GPS: noise by radio signals, atmospheric conditions, etc.
INFORMATION SYSTEM FOR OPERATORS BASED ON ANY SENSOR DEVELOPMENT IN ELES SLOVENIA 19
An Attempt to develop innovative TECHNOLOGY System based on Strain gauges DEVELOPMENT IN ELES, Slovenia, 2014 Measurements of fundamental frequency and deformation The measurement was carried out by sensors that were attached to the legs of the towers, namely: deformation gauges (resistance measuring gauges in longitudinal and transverse direction) and also the 20 accelerometer and temperature gauges-tower.
An Attempt to develop strain gauges approch 21
VISION ON OHL MONITORING AIDED BY SATELLITES CONDUCTOR: SAG, TEMPERATURE, ICING TOWERS: DEFORMATIONS CORRIDORS: VEGETATION MANAGEMENT PREDICTIONS GROUND LEVEL WIND FLOW RECOVERING SUPPORTS DURING LARGE WEATHER STORMS, SPACE STORMS 22
SOME CONCLUSIONS 1 Development of sensor technologies as well as ICT has resulted in the formation of the number of new monitoring technologies for OVERHEAD power lines. 2. DLR is the cheapest approach to increase capacity, but decision of technology needs very careful selection: method of data transfer and the accuracy of the sensor. 3. New innovative methods as strain gauges and differential Global Positioning Systems using satellites could be very promising technologies for OHLs. 23
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Approaches to predictive rating methods Using National Weather Service forecast? Or to develop own tool? 1. Persistence models and combination -(models are in class of easy predictions models - plain predictor) 2. Statistical approaches -(time-series analyses, ARIMA, wavelet,...) 3. Data mining approaches (ANN) - Next generation of wind forecasting technology (Regime switching space-time algorithms) 25
Comparison between real and predicted values for wind speed in two different S/S Autocorrelation function for wind speed 1,2 1 0,8 S/S 1 S/S 2 1,5 1 ACF 0,6 0,4 ACF 0,5 0,2 0-0,2 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76 Lag 0-0,5 1 11 21 31 41 51 61 71 81 91 101 111 121 131 141 151 161 171 Lag 45 input neurons, 10 hide, 1 output 52 input neurons, 20 hide, 1 output Wind speed (m/c) 7 6 5 4 3 2 Bericevo (Wind speed prediction: Feedforward network wih 45 inputs,10 in the hidden layer and 1 output) Real Prediction Wind speed m/c 6 5 4 3 2 Podlog (Wind speed prediction: Feedforward network wih 52 inputs,20 in the hidden layer and 1 output) Real Prediction 1 1 0 Time (22.01.06 00:00-28.01.06 23:55 ) 0 Time (22.01.06 00:00-28.01.06 23:55 ) Predictions for wind speed for 4 hours ANN method
Evaluation of flexible line capacity Present approach: - Fixed or seasonal OHL rating, - DLR using monitoring systems without predictions. Future approach: - Use of a new technology (ICT, protection schemes) and new mathematical modeling for predictions will enables dynamic evaluation of line capacity and flexible line capacity for trade, But take care: Maybe new type of HTLS conductors can offer you better flexibility for same cost or even cheaper.